(a) Field of the Invention
This invention relates to a bicycle hub assembly for holding a plurality of chain gear sprockets, commonly called a “cassette”, attached to a ratcheting cassette body, and more particularly, but not by way of limitation, to a hub assembly with a cassette body that is supported entirely by a hub shell itself. The hub assembly, used for supporting the cassette body, is designed to eliminate an unsupported span of a rear hub axle common on modern hubs. The benefits of this hub assembly design are: increased lateral rigidity of the rear hub axle, improved bearing durability, improved stiffness to weight ratio of the hub assembly, greater efficiency of torque transfer when applying pedal load to the hub assembly during the operation of a bicycle, and significant improvement to the lateral rigidity of the complete wheel.
(b) Discussion of the Prior Art
Modern day bicycle rear wheel hub assemblies include a cassette body mounted on an unsupported portion of an extended rear hub axle. The cassette body provides for “free wheeling” when coasting on the bicycle, and driving the bicycle when not coasting. The body makes for easy gear sprocket changes and customized gear ratios. But, because the rear hub axle is unsupported when extending outwardly from one side of the rear hub shell, load and alignment problems occur. For example, the extended hub axle span allows the hub axle to flex significantly under lateral and torsion loads. This flexing of the hub axle causes bearing misalignment, which in turn increases loaded drag and leads to premature bearing failure. Also, the flexing of the hub axle significantly reduces the lateral rigidity of the entire rear wheel.
Others have tried to reduce the above mentioned rear hub axle and bearing problems by the use of a stiffer hub axle, which in turn creates additional problems. A stiffer hub axle can be made of steel, rather than lightweight aluminum, with a thick wall to create a significant increase in stiffness. But this approach adds unnecessary weight to the hub assembly.
Another solution by others has been to use a large diameter aluminum hub axle, which can be made reasonably light and stiff. However, this feature requires the use of thin section bearings, which tend to wear out quickly or become damaged, which adds significant drag to the hub assembly.
Still another approach by others has been to use a separate bolt-on cassette body attached to one end of the rear hub assembly. In this example, the cassette body is excessively heavy with a ratchet driver housed inside the body. Because of the diameter constraints of the cassette cogs, the internal diameter of the cassette body is relatively small. Therefore, the ratchet driver inside the cassette body is reduced in size, severely limiting the strength and performance of the hub assembly.
The subject hub assembly, as described herein, provides clear-cut objects, advantages and unique structural features heretofore not incorporated into a rear wheel cassette style hub assembly to eliminate the above mentioned problems related to an unsupported rear hub axle span.